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Description

The Global River Radar Altimeter Time Series (GRRATS) are simulated river gauge data that are derived from ERS-1, ERS-2, TOPEX/Poseidon OSTM/Jason-2, Jason-3 and Envisat altimetric measurements. The purpose of these heights are to provide satellite altimetric river height data in a form that is more recognizable to the observational community and as a way to get users use to using satellite data for river hydrology. These pre SWOT data are derived from satellites to provide hydrological measurements. The Surface Water and Ocean Topography (SWOT) mission will have hydrology as one of its objectives. This dataset does not have the same variables as SWOT, but does provide hydrological measurements with typical quality flagging typical of satellite data. Not only does it provide science information, it can also assist hydrological users new to satellite data with the satellite data formats and variables before SWOT launches.If you are looking for version 1 it can be found at https://podaac.jpl.nasa.gov/dataset/PRESWOT_HYDRO_GRRATS_L2_VIRTUAL_STATION_HEIGHTS_V1 however this version should be used with caution. Version 2, this page, is the most recent version with the most accurate algorithms used for producing river heights.

Product Summary

Platforms
OSTM/JASON-2 ,
ERS-1 ,
ENVISAT ,
JASON-3 ,
JASON-1 ,
ERS-2
Instruments
POSEIDON-3 ,
ALTIMETERS ,
RA-2 ,
POSEIDON-3B ,
POSEIDON-2
Spatial Extent

N: 90 S: -90 E: 180 W: -180

Spatial Resolution
250 Meters x 500 Meters
Geographic Region
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
1992-04-06 to 2018-04-20
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C2036882009-POCLOUD
Data State
COMPLETE
Number of Files/Granules
1870
Processing Level
2
Published
Updated
Science Keywords
Surface Water Features

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

Coss, S., Durand, M., Lettenmaier, D., Yi, Y., Jia, Y., Guo, Q., Tuozzolo, S., Shum, C. K., Allen, G. H., Calmant, S., & Pavelsky, T. (2019). Pre SWOT Hydrology GRRATS Virtual Station River Heights Version 2 [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/PSGRA-SA2V2 Date Accessed: 2025-12-14

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
/Filter/icefreeze Freeze_dates_for_river N/A double N/A N/A 1
/Filter/icethaw Thaw_dates_for_river N/A double N/A N/A 1
/Filter/maxh Maximum_elevation_allowed_by_filter_above_EGM08_geoid m double N/A N/A 1
/Filter/minh Minimum_elevation_allowed_by_filter_above_EGM08_geoid m double N/A N/A 1
/Filter/nNODATA Number of Cycles without Data count int N/A N/A 1
/Filter/riverh This is the DEM based altitude of the VS location. Filter limits are constructed around this value (referenced to EGM08 Geoid) m double N/A N/A 1
/Sampling/island Flag for the presence of an island in the landsat scene used to draw the extracion polygon N/A int -1 N/A 1
/Sampling/latbox Latitude of the maximum extent of extraction polygon degree_north double N/A N/A 1
/Sampling/lonbox longitud of the maximum extent of extraction polygon degree_east double N/A N/A 1
/Timeseries/cycle The altimeter cycle for each pass. N/A int N/A N/A 1
/Timeseries/hbar Pass averaged and filtered river surface heights with respect to EGM08 Geoid) m double -9998 48.109666666667 to 58.11875 1
/Timeseries/hbarST Data have undergone statistical window filtering and outlier removal prior to height and ice filtering and pass averaging (referenced to EGM08 Geoid) m double -9998 48.109666666667 to 58.11875 1
/Timeseries/hwbar Sigma0 weighted pass average heights (referenced to EGM08 Geoid) m double -9998 48.317343238286 to 58.479481078201 1
/Timeseries/pkbar Pass averaged Peakiness - double N/A N/A 1
/Timeseries/sig0bar Pass averaged backscatter coefficient days since 1901-01-01T00:00:00 double N/A N/A 1
/Timeseries/time date where this VS froze days since 1901-01-01T00:00:00 double N/A N/A 1
/Unprocessed GDR Data/allfilter A flag that combines the other two. This flag will provide the heigts that are then averaged to create the final time series. N/A int N/A N/A 1
/Unprocessed GDR Data/cycle The cycle number of the measurement.These are pre-averaged GDR data. N/A int N/A N/A 1
/Unprocessed GDR Data/h These are pre-averaged GDR data with respect to EGM08 geoid m double -9998 19.291 to 58.966 1
/Unprocessed GDR Data/heightfilter Flag for GDR heights that passed the height filter.These are pre-averaged GDR data. N/A int N/A N/A 1
/Unprocessed GDR Data/icefilter A flag for measurements without ice. These are pre-averaged GDR data. N/A int N/A N/A 1
/Unprocessed GDR Data/lat latitude degrees_north double N/A N/A 1
/Unprocessed GDR Data/lon longitude degrees_east double N/A N/A 1
/Unprocessed GDR Data/pk The peakiness of the measurement.These are pre-averaged GDR data. N/A double N/A N/A 1
/Unprocessed GDR Data/sig0 Altimeter backscatter coefficient. These are pre-averaged GDR data dB double N/A N/A 1
/Unprocessed GDR Data/time time days since 1901-01-01T00:00:00 double N/A N/A 1
Flow_Dist This is the distance along the river centerline from the river mouth to this VS. km double N/A N/A 1
lat latitude degrees_north double N/A N/A 1
lon longitude degrees_east double N/A N/A 1
nse The best NSE evaluation for this VS. VS anomalies were compaired with all gages on the river. N/A double N/A N/A 1
nsemedian The median NSE evaluation for this VS. VS anomalies were compaired with all gages on the river. N/A double N/A N/A 1
nsemedianst The median NSE at this VS after statistical filtering. VS anomalies were compaired with all gages on the river. N/A double N/A N/A 1
nsest The highest NSE at this VS after statistical filtering. VS anomalies were compaired with all gages on the river. N/A double N/A N/A 1
pass The altimeter pass number that crosses this VS. N/A int N/A N/A 1
prox The river centerline distance to the nearest gage. m double N/A N/A 1
proxE Nash Sutcliffe efficiency of most proximal gage m double N/A N/A 1
proxR correlation coefficient of most proximal gage N/A double N/A N/A 1
proxSTD standard deviation of error of most proximal gage m double N/A N/A 1
R The highest correlation coefficient with this VS. VS anomalies were compaired with all gages on the river. N/A double N/A N/A 1
rate sampling rate of the altimeter Hz double N/A N/A 1
Rst The highest R at this VS after statistical filtering. VS anomalies were compaired with all gages on the river. N/A double N/A N/A 1
std The lowest standard deviation of error at this VS. VS anomalies were compaired with all gages on the river. m double N/A N/A 1
stdmedian The median standard deviation of error at this VS. VS anomalies were compaired with all gages on the river. m double N/A N/A 1
stdmedianst The median standard deviation of error at this VS after statistical filtering. VS anomalies were compaired with all gages on the river. m double N/A N/A 1
stdst The lowest standard deviation of error at this VS after statistical filtering. VS anomalies were compaired with all gages on the river. m double N/A N/A 1
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